Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder caused by mutations in the DMD gene with a prevalence of 1 in 3500 male births. The consequent loss of functional dystrophin results in the progressive degeneration of skeletal and cardiac muscle. Despite significant progress in our understanding of this disease and advances in the development of new therapeutic approaches, DMD remains a fatal disease. Much of what is known about DMD has come from studying dystrophin-deficient animals, particularly murine and canine models. While useful for mechanistic studies, dystrophic mice fail to develop the muscle weakness phenotype that is typical of DMD in patients. The canine models are more representative of human DMD, but are difficult to study due to extreme phenotypic variability. The canine models also suffer from a limited choice of mutations, significant expense, and social acceptance concerns. Therapeutic strategies that have shown promise in these models have yet to be successfully translated to the clinic. An animal model that more accurately and consistently replicates the clinical manifestations of human DMD is sorely needed. Our objective is to create an improved model of DMD in the pig. We believe a porcine model offers several advantages over the existing models. Gene targeting is now available in pigs and would provide an opportunity to engineer patient-relevant mutations. Porcine cloning technology would allow the production of genetically identical dystrophic pigs and could yield reduced variability in phenotype severity. Also, pigs are less expensive to produce and easier to house than dogs and don't face the same ethical concerns as companion animals. The ultimate goal of this project is to develop and commercialize DMD-targeted pigs as a model of Duchenne muscular dystrophy. We intend to accomplish this by combining gene targeting and somatic cell nuclear transfer to create a porcine model harboring a common human DMD mutation. This proposal outlines our plans for the creation and characterization of DMD-targeted pigs. Characterization will include an assessment of the molecular and biochemical consequences of dystrophin deficiency as well as a functional evaluation of the skeletal and cardiac muscle phenotype. We will also validate the DMD pig as a translational model by testing a nucleic acid-based therapy. This animal model will provide the academic and commercial research communities an opportunity to better understand DMD and to develop and test new therapeutic strategies